Lesson 20 Strategies for Dividing

- Let’s use different strategies to divide.

Warm-up Number Talk: Multiplication and Division

Find the value of each expression mentally.

$3 \times 5$
$6 \times 5$
$10 \times 5$
$65 \div 5$

Activity 1 Ways to Divide

Lin, Priya, and Tyler found the value of $78 \div 3$ . Their work is shown.

Lin

Priya

$\begin{aligned} 3 \times 10 & = 30 \\ 3 \times 10 & = 30 \\ 3 \times 6 & = 18 \\ \overset{―}{3 \times 26} & \overset{―}{= 78} \end{aligned}$

Tyler

$\begin{aligned} 3 \times 20 & = 60 \\ 3 \times 6 & = 18 \\ 20 + 6 & = 26 \end{aligned}$

Make sense of each student’s work.
How are the three students’ work alike?
How are they different?

Activity 2 How Would You Divide?

Problem 1

Find the value of each quotient. Explain or show your reasoning. Organize it so it can be followed by others.

$80 \div 5$
$68 \div 4$
$91 \div 7$

Problem 2

If you have time… Eighty-four students on a field trip are put into groups. Each group has 14 students. How many groups are there?

Activity 3 Compare, Divide within 100

Play Compare with 2 players.

Shuffle the cards and split the deck between the players.
Each player turns over a card.
Compare the values. The player with the greater value keeps both cards.
Play until you run out of cards. The player with the most cards at the end of the game wins.

Practice Problems

Problem 1

Find the value of $78 \div 6$ . Draw a diagram if it is helpful.
Find the value of $42 \div 3$ . Draw a diagram if it is helpful.

Problem 2

Find the value of each quotient.

$96 \div 6$
$87 \div 3$